Turbo blower and high speed rotating body used in same

ABSTRACT

The present invention relates to a turbo blower and a high speed rotation body used in the turbo blower. The turbo blower includes: i) a motor having a motor shaft; ii) a gear housing accommodating a bull gear fitted on the motor shaft and a pinion gear engaged with the bull gear; iii) a high speed rotation body that includes a rotary shaft having the pinion gear on the external circumferential surface, an impeller fitted on one end of the rotary shaft, and a rotation body housing accommodating the rotary shaft, the pinion gear, and at least one first composite bearing and partially cut off to expose the pinion gear, and is partially accommodated in the gear housing; and iv) a scroll portion covering the impeller and discharging compressed air.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Korean Patent Application No. 10-2008-0053860 and 10-2009-0035014 filed in the Korean Intellectual Property Office on Jun. 9, 2008 and Apr. 22, 2009, the entire contents of which are incorporated herein by reference,

BACKGROUND OF THE INVENTION

(a) Field of the Invention

The present invention relates to a turbo blower, and more particularly, to a turbo blower that can minimize axial load and radial load which are generated in operation, and a high speed rotation body used in the turbo blower.

(b) Description of the Related Art

Turbo blowers are high speed rotation bodies for acquiring large output from a small volume. The high speed rotation bodies can be classified, in accordance with the driven type, in a direct-driven type in which the rotation bodies are directly connected to a high-speed motor and an indirect-driven type in which the rotation bodies are connected to a common motor through a gear accelerator that increases the rotational speed.

The direct-driven type of high speed rotation bodies are supported by a common air bearing. However, the air bearing is limited in long time-use (e.g. over 3 years) because of low durability of the parts.

Common gear accelerators used for the indirect-driven type are composed of a bull gear fixed to the motor shaft and a pinion gear mounted on the high speed rotation body and engaged with the bull gear. However, it is required to improve the structure to reduce axial load and radial load that are exerted in the high speed rotation body and the bull gear when the turbo blowers equipped with the gear accelerators operate.

Further, since the turbo blowers equipped with the gear accelerators are provided with a gear box accommodating the bull gear and the pinion gear, it is necessary to horizontally divide the gear box itself and also horizontally divide the bearing supporting the shafts of the gears in manufacturing in order to assemble the gear box with the turbo machine.

Accuracy is a problem in manufacturing when dividing the gear box in manufacturing and it is difficult to achieve assembly accuracy when center the gear shafts for high speed rotation after the turbo machine is assembled. Further, the number of parts increases and the manufacturing cost increases.

The indirect-driven type of turbo blowers should be equipped with an oil pump to supply a lubricant, such that the number of parts increases. Further, since the bull gear and the motor shaft are fixed by shrink fit in the related art, it is difficult to disassemble and assemble the bull gear, when it needs to replace the bull gear due to abrasion.

The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.

SUMMARY OF THE INVENTION

The present invention has been made in an effort to provide a turbo blower having advantages of minimizing axial load and radial load exerted in a high speed rotation body and a bull gear.

Further, the present invention has been made in an effort to provide a turbo blower having advantages of being able to circulate and supply a lubricant to the high speed rotation body without using an oil pump supplying the lubricant by using an oil circulation structure in the turbo blower.

Further, the present invention has been made in an effort to provide a turbo blower having advantages of simplifying assembly and disassembly of the high speed rotation body, the bull gear, and a motor.

An exemplary embodiment of the present invention provides a turbo blower including: i) a motor having a motor shaft; ii) a gear housing accommodating a bull gear fitted on the motor shaft and a pinion gear engaged with the bull gear; iii) a high speed rotation body that includes a rotary shaft having the pinion gear on the external circumferential surface, an impeller fitted on one end of the rotary shaft, and a rotation body housing accommodating the rotary shaft, the pinion gear, and at least one first composite bearing and partially cut off to expose the pinion gear, and is partially accommodated in the gear housing; and iv) a scroll portion covering the impeller and discharging compressed air.

The first composite bearing may include: i) a composite bearing block integrally having a sliding bearing block and a ball bearing block; ii) a sliding bearing shaft formed on the external circumferential surface of the rotary shaft and accommodated in the sliding bearing block to form a sliding bearing together with the sliding bearing block; and iii) a ball bearing accommodated in the ball bearing block.

The first composite bearing may be positioned at both sides of the pinion gear and a predetermined gap of the sliding bearing may be larger than a predetermined gap of the ball bearing. The sliding bearing shaft may have a plurality of oil grooves for forming an oil film on the surface and a plurality of taper grooves which are formed at an angle, and the sliding bearing block may have a side pressure-absorbing groove at the portion facing the bull gear, in the inner surface and absorb side pressure due to the bull gear.

The high speed rotation body may have a vent hole formed at the end of the rotation body housing which faces the impeller, the pinion gear may be formed in a helical gear shape, and the direction of the helical gear may be determined such that a force attracting the rotary shaft in opposite direction to the impeller when the rotary shaft rotates.

The gear housing may have an arc-shaped guide cover having a plurality of oil guide grooves on the inner surface while covering a portion of the bull gear, and an oil box connected with the end of the guide cover at the upper portion therein.

The gear housing may have an oil pipe therein to supply lubricant collecting in the oil box to the first composite bearing, one end of the oil pipe may be connected with an oil outlet formed in the oil box, and the other end of the oil pipe may be connected with an oil inlet formed in the first composite bearing.

The rotation body housing may have a vapor outlet for discharging oil vapor and the turbo blower may further include an oil vapor cooler connected with the vapor outlet and the oil box. The oil vapor cooler may supply the oil vapor discharged to the vapor outlet to the oil box after condensing the oil vapor.

The gear housing may have an oil reservoir at the lower portion, the oil reservoir may have a pair of holes at the upper and lower portion of the side wall, and the gear housing may further include a connection pipe connecting the pair of holes and a control valve disposed in the connecting pipe.

The bull gear may be directly fitted on the motor shaft, the gear housing may have a combining surface with an opening larger than the diameter of the bull gear, at the side facing the motor, and the combining surface may be combined with the motor.

Another exemplary embodiment of the present invention provides a high speed rotation body including: i) a rotary shaft having a pinion gear engaged with a bull gear, on the external circumferential surface; ii) an impeller fitted on one end of the rotary shaft; iii) a pair of first composite bearings disposed at both sides of the pinion gear; and iv) a rotation body housing accommodating the rotary shaft, the pinion gear, and the pair of first composite bearings, and partially cut off to expose the pinion gear.

Each of the pair of first composite bearings may include: i) a composite bearing block integrally having a sliding bearing block and a ball bearing block; ii) a sliding bearing shaft formed on the external circumferential surface of the rotary shaft and accommodated in the sliding bearing block to form a sliding bearing together with the sliding bearing block; and iii) a ball bearing accommodated in the ball bearing block.

A predetermined gap of the sliding bearing may be larger than a predetermined gap of the ball bearing, the sliding bearing shaft may have a plurality of oil grooves for forming an oil film on the surface and a plurality of taper grooves which are formed at an angle, and the sliding bearing block may have a side pressure-absorbing groove formed in the opposite direction to the direction of side pressure in order to absorb the side pressure due to the bull gear, on the inner surface.

Yet another exemplary embodiment of the present invention provides a turbo blower including: i) a motor having a motor shaft; ii) a bull gear detachably fitted on the motor shaft and having a hole for mounting a fixing shaft at the center; iii) a second composite bearing disposed between the fixing shaft and the bull gear and having a taper roller bearing and a ball bearing that are parallel with the motor shaft; and iv) a high speed rotation body having a rotary shaft with a pinion gear engaged with the bull gear, on the external circumferential surface, and an impeller fitted on one end of the rotary shaft.

The turbo blower may further includes: i) a motor cover fastened to the motor and supporting the motor shaft; and ii) a gear housing accommodating the bull gear and the pinion gear and having an opening having a diameter larger than the diameter of the bull gear, at the side fastened to the motor cover.

The motor shaft may have a flange on the external circumferential surface of the end facing the bull gear, the bull gear may be fastened to the motor shaft by a plurality of bolts passing through the bull gear and the flange, and the gear housing may have an opening at the portion facing any one bolt in the plurality of bolts. The motor cover may have a recess protruding toward the motor to accommodate a portion of the high speed rotation body in the recess.

The high speed rotation body may further include: i) a pair of first composite bearing disposed at both sides of the pinion gear; and ii) a rotation body housing accommodating the rotary shaft and the pair of first composite bearing, assembled with the gear housing, and partially cut off to expose the pinion gear in the gear housing.

Each of the first composite bearings may include: i) a composite bearing block integrally having a sliding bearing block and a ball bearing block; ii) a sliding bearing shaft formed on the external circumferential surface of the rotary shaft and accommodated in the sliding bearing block to form a sliding bearing together with the sliding bearing block; and iii) a ball bearing accommodated in the ball bearing block.

A predetermined gap of the sliding bearing may be larger than a predetermined gap of the ball bearing and the sliding bearing shaft may have a plurality of oil grooves for forming an oil film on the surface and a plurality of taper grooves which are formed at an angle.

The gear housing may have an arc-shaped guide cover covering a portion of the bull gear, on the inner surface, and a stepped protrusion positioned on the outer surface of the side of the bull gear, and the protrusion may form a temporary reservoir in an assembly of the gear housing and the motor cover.

The guide cover may have a plurality of oil guide grooves connected long in the rotation direction of the bull gear, on the inner surface. The gear housing may further include a first through-hole at the portion where the temporary reservoir is formed and a first oil pipe connecting the first through-hole with the fixing shaft at the outside of the gear housing.

The fixing shaft may be fastened to the gear housing, the fixing shaft may have an oil holes therein, and an oil channel may be formed between the fixing shaft and the motor shaft, such that lubricant supplied to the oil hole is guided to the second composite bearing.

The protrusion may have a second through-hole at the lower end, the gear housing may have a third through-hole at the joint with the rotary shaft housing, and a second oil pipe connecting the first through-hole with the third through-hole in the gear housing may be further included.

The rotation body housing may have an oil channel connecting the first composite bearing at the impeller in the pair of first composite bearing with the third through-hole, and may further include a third oil pipe connecting the first composite bearing at the opposite side of the impeller in the pair of first composite bearing with the oil channel at the outside thereof.

The high speed rotation body may further include a support body disposed between the first composite bearing at the impeller and the impeller, the support body and the rotation body housing may form an oil outlet, and the rotation body housing may further include a fourth oil pipe connecting the oil outlet with the gear housing at the outside to collect the lubricant.

The turbo blower may further include: i) a bearing and a sealing member that are disposed in parallel away from the bull gear, on the external circumferential surface of the motor shaft; and ii) a fifth oil pipe connecting the sealing member with the inside of the motor cover to collect lubricant reaching the sealing member.

Still another exemplary embodiment of the present invention provides a turbo blower including: i) a motor having a motor shaft and assembled with a motor cover; ii) a bull gear detachably fitted on the motor shaft and having a hole for mounting a fixing shaft at the center; iii) a high speed rotation body including a rotary shaft having a pinion gear engaged with the bull gear, on the external circumferential surface, an impeller fitted on one end of the rotary shaft, at least one first composite bearing supporting the rotary shaft, and a rotation body housing accommodating the rotary shat and the first composite bearing and partially cut off to expose the pinion gear; iv) a second composite bearing disposed between the fixing shaft and the bull gear and having a taper roller bearing and a ball bearing that are parallel with the motor shaft; v) a gear housing accommodating the bull gear and the pinion gear and having an opening having a diameter larger than the diameter of the bull gear, at the side fastened to the motor cover; and vi) a scroll portion covering the impeller and discharging compressed air.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of a turbo blower according to the first exemplary embodiment of the present invention.

FIG. 2 is a left side view of the turbo blower shown in FIG. 1.

FIG. 3 is a perspective view of a gear housing in the turbo blower shown in FIG. 1, seen from an impeller.

FIG. 4 is a perspective view of the gear housing in the turbo blower shown in FIG. 1, seen from a motor.

FIG. 5 is a cross-sectional view of a high speed rotation body in the turbo blower shown in FIG. 1.

FIG. 6 is a front view showing a rotary shaft of the turbo blower shown in FIG. 1.

FIG. 7 is a schematic view showing a lubricant circulation system by using a front cross-sectional view and a side cross-sectional view of the gear housing in the turbo blower shown in FIG. 1 and a cross-sectional view of the high speed rotation body.

FIG. 8 is a top plan view of a turbo blower according to the second exemplary embodiment of the present invention.

FIG. 9 is a cross-sectional view of a motor shaft and a bull gear in the turbo blower shown in FIG. 8, seen in the direction A.

FIG. 10 is a partial enlarged view of FIG. 9.

FIG. 11 is a partial enlarged view showing the gear housing and the bull gear in the turbo blower shown in FIG. 8.

FIG. 12 is a perspective view of a motor cover in the turbo blower shown in FIG. 8, seen in the direction B.

FIG. 13 is a perspective view of the gear housing in the turbo blower shown in FIG. 8, seen in the direction C.

FIG. 14 is a cross-sectional view taken along the line I-I of FIG. 13.

FIG. 15 is a front view of the gear housing shown in FIG. 13, seen in the direction D.

FIG. 16 is a front view of the turbo blower shown in FIG. 8, seen in the direction C.

FIG. 17 is a right side view of the turbo blower of FIG. 8, seen in the direction B.

FIG. 18 is a front view showing the high speed rotation body in the turbo blower shown in FIG. 8.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The present invention will be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention.

FIG. 1 is a front view of a turbo blower 100 according to the first exemplary embodiment of the present invention, with a high speed rotation body 20 cut. FIG. 2 is a left side view of the turbo blower 100 shown in FIG. 1.

Referring to FIGS. 1 and 2, the turbo blower 100 according to the first exemplary embodiment includes a support plate 10, a motor 11, a gear housing 12, and a scroll portion 13. The motor 11 and the gear housing 12 are fixed on the support plate 10 and a portion of a high speed rotation body 20, which is described below, is positioned in the gear housing 12.

A motor shaft 14 connected to the motor 11 and a rotary shaft 21 of the high speed rotation body 20 are not directly connected, but eccentrically positioned in the turbo blower 100 of the first exemplary embodiment. That is, a bull gear 15 is directly fitted on the motor shaft 14 and a pinion gear 16 is formed on the rotary shaft 21, such that the bull gear 15 and the pinion gear 16 are engaged and increase power from the motor 11 to operate the high speed rotation body 20.

The first exemplary embodiment can remove a bull gear shaft supporting the bull gear in gear boxes for increasing speed of the related art, does not need to seal the potion between the motor and the gear box, and reduce the number of parts by using a power transmission structure described above, thereby reducing the manufacturing cost.

As described above, in order to directly fit the bull gear 15 on the motor shaft 14, as shown in FIGS. 3 and 4, a gear housing 12 is integrally manufactured and one side of the gear housing 12 which is connected with the motor 11 is formed to be open, larger than the diameter of the bull gear 15. Further, a bracket 17 is mounted to the motor 11 to fasten the gear housing 13.

FIG. 3 is a perspective view of the gear housing 12 in the turbo blower 100 shown in FIG. 1, seen from an impeller 22 and FIG. 4 is a perspective view of the gear housing 12 in the turbo blower 100 shown in FIG. 1, seen from the motor 11.

In FIG. 3, reference numeral ‘121’ indicates a first combining surface for fasten the high speed rotation body 20 and the scroll portion 13 to the gear housing 12. In FIG. 4, reference numeral ‘122’ indicates a second combining surface for fastening the gear housing 12 to the bracket 17 of the motor 11.

The high speed rotation body 20 or the bracket 17 of the motor 11 may be fastened to the first and second combining surfaces 121 and 122 of the gear housing 12 by common mechanical methods, such as using bolts and nuts. Further, common sealing members, such as a rubber pad, for sealing the inside by blocking the outside and the inside of the gear housing 12 is provided on the first and second combining surfaces 121 and 122, and the combining method and the sealing members are typical and the detailed description is not provided.

It is possible to assemble the bull gear having a large diameter with the motor shaft 14 first, assemble the second combining surface 122 of the gear housing 12 with the bracket 17 of the motor 11, and then sequentially assemble the high speed rotation body 20 and the scroll portion 13 with the first combining surface 121 of the gear housing 12 in the assembly process, by providing the gear housing 12.

The high speed rotation body 20 is described hereafter in detail with reference to FIG. 5. FIG. 5 is a cross-sectional view showing the high speed rotation body 20 of the turbo blower 100 shown in FIG. 1, in which the portion indicated by dotted lines is an exploded view showing only a first composite bearing 26.

Referring to FIG. 5, the high speed rotation body 20 includes a rotary shaft 21, a rotation body housing 23 accommodating the rotary shaft 21, a pair of first composite bearings 26 integrally formed with a sliding bearing 24 and a bail bearing 25, and an impeller 22 fitted on one end of the rotary shaft 21.

The rotation body housing 23 is formed substantially in a cylindrical shape in an integral type, different from the separation type, which is used for common high speed rotation body. The rotation body housing 23 is cut at the portion where the pinion gear 16 formed on the rotary shaft 21 is positioned such that the pinion gear 16 is exposed outside the rotation body housing 23. The pinion gear 16 exposed as described above is engaged with the bull gear 15 in the gear housing 12.

A flange 27 is formed at the middle portion of the rotation body housing 23 and a plurality of fastening holes 217 is formed through the flange 27, such that the rotation body housing 23 can be assembled with the with the first combining surface 121 of the gear housing 12. Further, the rotation body housing 23 has a plurality of holes for supplying and discharging a lubricant to the first composite bearing 26. The holes are described below.

The first composite bearings 26 are positioned at both sides of the pinion gear 16 formed on the rotary shaft 21. The first composite bearing 26 is configured such that a sliding bearing shaft 241 and a ball bearing 25 are disposed in one composite bearing block 28.

As indicated by the dotted lines in FIG. 5, the first composite bearing 26 includes a composite bearing block 28, the sliding bearing shaft 241, and the ball bearing 25. The composite bearing block 28 integrally has a sliding bearing block 281 and a ball bearing block 282. The sliding bearing block 241 is formed on the external circumferential surface of the rotary shaft 21, and accommodated in the sliding bearing block 281 to form the sliding bearing 24 together with the sliding bearing block 281. The ball bearing 25 is accommodated in the ball bearing block 282. The ball bearing 25 includes balls 251 directly carrying load in a low-speed operation, and an outer race 252 and an inner race 253 which retain the balls 251.

In the portion indicated by the dotted lines in FIG. 5, reference numeral ‘261’ designates a ring fastened between the composite bearing block 28 and the rotation body housing 23 and reference numeral ‘262’ designates a fastening ring for fastening the ball bearing 25 to the composite bearing block 28. Further, reference numeral ‘263’ designates a nut for fixing the rotary shaft 21 to the composite bearing block 28.

The reason o fusing the first composite bearings 26 for the high speed rotation body 20 in the turbo blower 100 of the first exemplary embodiment is as follows.

If only a sliding bearing is used in the high speed rotation body, although it is possible to carry large load by using pressure of oil which is generated by high-speed rotation, the sliding bearing block and the rotary shaft are in direct contact in starting, stopping, or operating at low speed, not in the high-speed rotation. Therefore, the start is difficult and heat and abrasion are generated by friction, such that it is required to forcibly supply a lubricant, using an oil pump, in order to remove the problems.

On the contrary, when only a ball bearing is used in the high speed rotation body, although it is possible to remove the problem due to friction in starting, stopping, or operating at low speed and it is possible to supply only an un-pressure lubricant without an oil pump, the ball bearing carries large load in a high-speed rotation, such that the durability is deteriorated.

Therefore, it is possible to remove all of the problems by providing the first composite bearings 26 composed of the sliding bearing 24 and the ball bearing 25 to the high speed rotation body 20, in the turbo blower 100 of the first exemplary embodiment.

As described above, when the high speed rotation body 20 is provide with the first composite bearings 26, the rotary shaft 21 and the composite bearing block 28 do not come in direct contact by the ball bearing 25, for the structural features. Therefore, in the turbo blower 100, the high speed rotation body 20 operating is supported by the ball bearing 25 in the early low-speed operation while the high speed rotation body 20 operating can be supported by the sliding bearing 24 in a high-speed operation.

In accordance with the structure of the first composite bearing 26, carrying load is automatically changed in accordance with the operation regions (rotation speed) when the high speed rotation body 20 operates.

For this configuration, a predetermined gap of the sliding bearing 24 is set larger than a predetermined gap of the ball bearing 25. In this configuration, the predetermined gap of the sliding bearing 24 implies a difference between the diameter of the internal surface of the sliding bearing block 281 and the diameter of the sliding bearing shaft 241 and the predetermined gap of the ball bearing 25 implies a limit of the diameter of the ball 251 in the difference between the internal diameter of the outer race 252 and the external diameter of the inner race 253.

According to an example of the difference between the predetermined gaps, when the predetermined gap of the sliding bearing 24 is 0.2 mm, the predetermined gap of the ball bearing 25 may be 0.1 mm.

The principle of automatic change of carrying load in accordance with the operation regions (rotation speed) in the first composite bearing 26 when the high speed rotation body 20 operates is the same as that in the bearing assembly disclosed in Korean Patent Registration No. 10-0723040 by the applicant(s), and the detailed description is not provided.

On the other hand, the sliding bearing 24 of the first composite bearing 26 in the first exemplary embodiment may form an oil film without using a specific oil pump. This is described hereafter with reference to FIG. 6.

FIG. 6 is a front view showing the rotary shaft 21 of the turbo blower 100 shown in FIG. 1, with a left side view and a right side view of the rotary shaft 21.

Referring to FIG. 6, a plurality of oil grooves 242 and a plurality of taper grooves 243 are formed on the surface of the sliding bearing shaft 241 formed at the rotary shaft 21 to supply oil. The oil grooves 242 and the taper groove 243 are formed at an angle to the rotary shaft 21. The inclination direction of the oil grooves 242 and the taper groove 243 at one side of the pinion gear 16 is opposite to the inclination direction of the oil grooves 242 and the taper groove 243 at the other side of the pinion gear 16. Further, the taper grooves 243 are each depth at the portion contacting the oil grooves 242 and the depth decreases away from the oil groove 242.

As described above, the oil grooves 242 formed on the surface of the bearing shaft 241 are used to supply oil and the taper groove 243 are used to form an oil film by generating pressure in the oil supplied to the oil grooves 242. Therefore, the oil grooves 242 and the taper grooves 243 function the same oil pump, when the rotary shaft 21 rotates.

That is, as the rotary shaft 21 is rotated at high speed, a wedging effect is caused in the rotation direction and some of the oil generates high pressure in the sliding bearing 24 by means of centrifugal force. As a result, the rotary shaft 21 is floated and separated from the sliding bearing block 281, and the floated rotary shaft 21 can rotate at high speed. In this state, as the rotary shaft 21 rotates at high speed, the ball bearing 25 does not function as a bearing (that is, not in contact with the rotary shaft 21), and consequently the life span of the high speed rotation body 20 can be increased.

Therefore, the problems due to friction and pressure of the lubricant at high speed can be removed only by supplying the lubricant to the first composite bearings 26 without an oil pump, in the turbo blower 100.

Meanwhile, since the turbo blower 100 uses a structure increasing the rotation speed of the rotary shaft 21 by using the bull gear 15 and the pinion gear 16, side pressure is necessarily generated by the operation of the gears. The side pressure is generally applied from the bull gear 15 having a large diameter to the pinion gear 16 having a small diameter and the substantially direction of the side pressure is not the three o'clock direction perpendicular to the vertical line of the center of the rotary shaft 21, but about the five o'clock direction lower than the above direction.

Therefore, a means is required to absorbing the side pressure exerted in the pinion gear 16 of the rotary shaft 21. For this configuration, a side pressure-absorbing groove 29 (see the portion indicated by the dotted lines in FIG. 5) is formed in the inner surface of the sliding bearing block 281. The side pressure-absorbing groove 29 is formed at the portion facing the bull gear 15 (opposite to the direction of the side pressure), in the inner surface of the sliding bearing block 281. The length and depth of the side pressure-absorbing groove 29 are determined by calculating load according to the specification of the high speed rotation body 20. The side pressure-absorbing groove 29 may be formed in an arc shape below 180°.

An oil film is not formed where the side pressure-absorbing groove 29 is formed, but formed at the opposite side where the side pressure is exerted, in the composite bearing block 28. Therefore, the side pressure due to the bull gear 15 is removed and smooth rotation can be performed at high speed.

A method of removing radial load of the high speed rotation body 20 has been described above. However, axial load is exerted in the high speed rotation body 20 by a difference in pressure applied to the inlet and the outlet of the impeller 22, when the high speed rotation body 20 rotates at high speed. Therefore, a method of removing the axial load exerted in the high speed rotation body 20 is described hereafter.

The impeller 22 is disposed at one side of the rotary shaft 21 (the left in FIG. 5) in the high speed rotation body 20. In this case a negative pressure (−) is generated at the inlet of the impeller 22 and a positive pressure (+) is generated at the outlet of the impeller 22. Therefore, axial load is generated toward the impeller 22 with respect to the rotary shaft 21 (the left in FIG. 5).

The is, in order to remove the axial load, in the first exemplary embodiment, {circle around (1)} a vent hole 231 is formed at the end of the rotation body housing 23 which faces the impeller 22, {circle around (2)} the helical gear direction of the pinion gear 16 formed on the rotary shaft 21 is adjusted, and {circle around (3)} the ball bearing 25 is disposed in the composite bearing block 28.

The positive pressure (+) generated behind the impeller 22 is removed by the vent hole 231 of the rotation body housing 23. The pinion gear 16 is formed in a helical gear shape. The direction of the helical gear is determined such that the rotary shaft 21 is attracted opposite to the impeller 22 when rotating (the right in FIG. 5) to remove the axial load. if needed, the axial load is reduced by using basic axial load-carrying force of the ball bearing 25.

Next, a lubricant circulation system of the turbo blower 100 is described with reference to FIG. 7. The lubricant circulation system supplies a lubricant to the high speed rotation body 20 without using an oil pump.

FIG. 7 is a schematic view showing a lubricant circulation system by using a front cross-sectional view and a side cross-sectional view of the gear housing 12 in the turbo blower 100 shown in FIG. 1 and a cross-sectional view of the high speed rotation body 20.

Referring to FIG. 7, a guide cover 30 that covers the bull gear 15 is formed on the inner surface of the gear housing 12. A plurality of oil guide groove 301 is formed on the guide cover 30. Further, an oil box 31 connected with the end of the guide cover 30 is formed at the upper portion in the gear housing 12.

Therefore, as the bull gear 15 rotates, the lubricant in an oil reservoir 32 at the lower portion of the gear housing 12 is scattered by the teeth of the bull gear 15 and moves along the guide cover 30 and the oil guide groove 301, and then it drops down and collects in the oil box 31 by the gravity. In this operation, the lubricant remaining on the surface of the bull gear 15 lubricates the bull gear 15 and the pinion gear 16, when the bull gear 15 and the pinion gear 16 come in contact.

Some of the lubricant collecting in the oil box 31 is discharged to the oil outlet 311 by the gravity and supplied to the oil supply holes 232 formed in the rotation body housing 23 of the high speed rotation body 20 along an oil pipe.

The lubricant supplied to the oil supply holes 232 of the rotation body housing 23 is divided in two directions, such that some of the lubricant is supplied to the ball bearing 25 and most of the lubricant is supplied to the sliding bearing 24. The lubricant supplied to the sliding bearing 24 forms a pressurized oil film by the taper groove 243 formed on the sliding bearing shaft 241 while the rotary shaft 21 rotates at high speed to support the rotary shaft 21. The lubricant used for the sliding bearing 24 moves in opposite direction to the supply direction, and is discharged to the cut portion of the rotation body housing 23 for exposing the pinion gear 16 and then drops down into the oil reservoir 32 at the lower potion of the gear housing 12.

Meanwhile, as the high speed rotation body 20 rotates at high speed, the lubricant supplied to the first composite bearing 26 can produce oil vapor while vaporizing.

The oil vapor is discharged into the gear housing 12 and outside the gear housing 12, with respect to the flange 27 of the rotation body housing 23. The oil vapor discharged into the gear housing 12 is supplied again to the first composite bearing 26 by the lubricant circulation structure, such that it does not cause a specific problem, but the vapor discharged outside the gear housing 12 should be processed.

Some of the oil vapor discharged outside the gear housing 12, toward the impeller 22, from the first composite bearing 26 is condensed and the other is kept is the vapor state

The condensed lubricant is returned to the oil return hole 33 of the oil reservoir 32 through return holes 233. Further, the oil vapor kept in the vapor state is discharged through oil exhaust holes 234, and then condensed in an oil vapor cooler 34 and supplied again to the oil box 31 through a condensed oil supply hole 35 of the oil box 31.

As described above, the lubricant supplied to the oil box 31 through the condensed oil supply hole 35 returns to the oil reservoir 32 through the oil pipe 36 and a small amount of oil vapor remaining in the oil box 31 is discharged outside through an exhaust hole 37 of the oil box 31. A separator 38 having the top open and a through-hole therein is disposed in the oil box 31. Therefore, the oil box 31 can roughly separate the lubricant collected by the guide cover 30 and the oil guide groove 301 from the condensed lubricant supplied from the oil vapor cooler 34, and temporarily store the lubricants.

Meanwhile, the lubricant is stored in the oil reservoir 32 formed by closing the gear housing 12 and holes are formed at the upper and lower portions of the side wall of the oil reservoir 32. Further, a control valve 39 is disposed in a connection pipe that connects them. Therefore, it is possible to keep an appropriate amount of lubricant for operating the high speed rotation body 20 in the oil reservoir 32 by controlling the control valve 39.

In more detail, a large amount of lubricant is needed in consideration of scattering of the lubricant when the high speed rotation body 20 initially operates, but the lubricant in the oil reservoir 32 is exhausted, if the control valve 39 is closed. Therefore, it is possible a desired amount of lubricant for operating the high speed rotation body 20 by appropriately controlling the amount of lubricant supplied to the control valve 39.

In FIG. 7, reference numeral ‘40’ designates a pressure control valve that communicates with the vent hole 231 and controls a difference in pressure before and after the impeller 22.

FIG. 8 is a partial-cut top plan view of a turbo blower 110 according to the second exemplary embodiment of the present invention. The same components in the first exemplary embodiment described above are designated by the same reference numerals.

Referring to FIG. 8, the turbo blower 110 of the second exemplary embodiment includes a motor shaft 14, a bull gear 15, a high speed rotation body 20, and a second composite bearing 42.

The motor shaft 14 is connected to the motor 11 to rotate at high speed when the motor 11 operates. The bull gear 15 is detachably fitted on the motor shaft 14 and has a hole at the center where a fixing shaft 41 and the second composite bearing 42 are positioned. The high speed rotation body 20 includes a rotary shaft 21 where a pinion gear 16 engaged with the bull gear 15 is formed and an impeller 22 fitted on one end of the rotary shaft 21.

The turbo blower 110 further includes a motor cover 43, a gear housing 120, an inlet guide vein 44, and a scroll portion 13. The motor cover 43 is fastened to the front of the motor 11 facing the impeller 22 and the gear housing 120 is fastened to the front of the motor cover 43 facing the impeller 22. The entire bull gear 15 and the motor shaft 14 and a portion of the high speed rotation body 20 are positioned in the assembly of the motor cover 43 and the gear housing 120. The inlet guide vein 44 is disposed in an intake channel and adjusts the flow rate of a gas flowing into the impeller 22.

As the motor shaft 14 is rotated by operation of the motor 11, the bull gear 15 and the pinion gear 16 rotate and increase power from the motor 11, thereby operating the high speed rotation body 20. Therefore, the external gas flows into the rotating impeller 22 through the intake channel and is accelerated and compressed through the impeller 22, and then the compressed gas is discharged to the scroll portion 13 through a diffuser. FIG. 8 shows the intake direction and the exit direction of a gas with arrows.

In the operation of the turbo blower 110 described above, radial load is exerted in the bull gear 15 by the weight of the bull gear 15 and a force of the pinion gear 16 that pushes the bull gear 15, and axial load is generated by the helical shape of the bull gear 15 and the pinion gear 16. The second composite bearing 42, which is described below, effectively reduces the radial load and the axial load which are exerted in the bull gear 15 by supporting the bull gear 15, inside the bull gear 15.

FIG. 9 is a cross-sectional view of the motor shaft 14 and the bull gear 15 in the turbo blower 110 shown in FIG. 8, seen in the direction A and FIG. 10 is a partial enlarged view of FIG. 9.

Referring to FIGS. 9 and 10, the second composite bearing 42 is disposed in parallel with the motor shaft 14 between the fixing shaft 41 and the bull gear 15, and includes a taper roller bearing 45 and a ball bearing 46. The taper roller bearing 45 includes a roller 451 fitted in an inclination direction, and an inner race 452 and an outer race 453 which retain the roller 451. The ball bearing 46 includes balls 461, and an inner race 462 and an outer race 463 that retain the balls 461. The inner race 462 is fitted on the fixing shaft 41 and the outer race 463 is combined with the bull gear 15.

The taper roller bearing 45 simultaneously reduces radial load and axial load which are exerted in the bull gear 15 and the bull bearing 46 secondarily reduces the radial load exerted in the bull gear 15. Therefore, the turbo blower 110 of the second exemplary embodiment minimizes the radial load and the axial load which are exerted in the bull gear 15, using the second composite bearing 42. As a result, it is possible to preclude noise, abrasion of the bull gear 15, and deformation of the motor shaft 14, due to motion of the bull gear 15.

The fixing shaft 41 is fastened to a gear housing 120 by a fixing block 47 and bolts 48, with the center aligned with the center of the motor shaft 14. An oil hole 411 is formed in parallel with the fixing shaft 41 in the fixing shaft 41 to supply a lubricant to the second composite bearing 42. In this configuration, a predetermined gap is defined between the fixing shaft 41 and the motor shaft 14, such that a channel that guides the lubricant to the second composite bearing 42 is formed.

Meanwhile, the motor shaft 14 does not overlap the bull gear 15 and a flange 141 is fixed to the external circumferential surface of the end of the motor shaft 14 which faces the bull gear 15. The bull gear 15 may be fastened to the motor shaft 14 by a mechanical method using a plurality of bolts 49 that are inserted through the bull gear 15 and the flange 141. In this case, the bull gear 15 is detachably fitted on the motor shaft 14, not permanently, such as shrink-fitting, it is possible to easily assemble and disassembly the bull gear 15 and the motor shaft 14 in order to replace of manage the bull gear 15.

FIG. 11 is a partial enlarged view showing the gear housing 120 and the bull gear 15 in the turbo blower 110 shown in FIG. 8.

Referring to FIG. 11, the gear housing 120 has an opening 123 at a portion that faces one bolt 49 in the bolts 49. The bolt 49 can be removed by putting a tool (not shown) into the opening 123. That is, the bolt 49 is removed by a tool, and then another bolt 49 is positioned at the opening 123 by manually turning the bull gear 15 and then the bolt 49 is removed by putting the tool in. All of the bolts 49 can be removed by repeating this process.

The bull gear 15 with all the bolts 49 removed is supported by the second composite bearing 42, in which it is possible to easily disassemble the motor 11 and the motor shaft 14 from the bull gear 15 and the gear housing 120 by separating the motor cover 43 from the gear housing 120.

In the turbo blower 110 of the second exemplary embodiment, the configuration and operation of the high speed rotation body 20 and the first composite bearing 26 are the same as those in the first exemplary embodiment described above, such that the detailed description is not provided.

Next, the shapes of the motor cover 43 and the gear housing 120 are described.

FIG. 12 is a perspective view of the motor cover 43 in the turbo blower 110 shown in FIG. 8, seen in the direction B.

Referring to FIGS. 8 and 12, the motor cover 43 has a space 431 accommodating the motor shaft 14 and a third combining surface 432 formed around the space 431 to be fastened to the motor 11. Further, the motor cover 43 has a recess 50 protruding toward the motor 11 to enlarge the space in the assembly of the motor cover 43 and the gear housing 120 to the motor 11.

The larger the capacity of the turbo blower 110, the more the length of the rotary shaft 21 increases, such that a space for accommodating the rotary shaft 21 is required. According to the turbo blower 110 of the second exemplary embodiment, since the recess 50 is formed on the motor cover 43, the opposite side to the impeller 22 in the high speed rotation body 20 can be accommodated in the recess 50, such that the large high speed rotation body 20 can also be easily disposed.

FIG. 13 is a perspective view of the gear housing 120 in the turbo blower 110 shown in FIG. 8, seen in the direction C and FIG. 14 is a cross-sectional view taken along the line I-I of FIG. 13.

Referring to FIGS. 13 and 14, the gear housing 120 is formed with the portion fastened to the motor cover 43 opened larger than the diameter of the bull gear 15. That is, the gear housing 120 has a vertical wall 51 defining two holes for accommodating the fixing shaft 41 of the bull gear 15 and the high speed rotation body 20 and a side wall 52 enlarged from the edge of the vertical wall 51 toward the motor cover 43, in which the portions fastened to the motor cover 43 are open.

Therefore, as shown in FIG. 8, the bull gear 15 and the motor shaft 14 are assembled, the gear housing 120 is fastened to the motor cover 43 to cover the bull gear 15, the fixing shaft 41 and the high speed rotation body 20 are assembled with the gear housing 120, and the scroll portion 13 is assembled with the rotation body housing 23. Disassembling is made in the opposite order to the assembly order. The turbo blower 110 can be easily assembled and disassembled by the detachable structure of the motor shaft 14 and the bull gear 15 and the shape of the gear housing 120 having a large open side.

Next, a lubricant circulation system of the turbo blower 110 according to the second exemplary embodiment is described.

FIG. 15 is a front view of the gear housing 120 shown in FIG. 13, seen from the direction D.

Referring to FIGS. 14 and 15, a substantially arc-shaped guide cover 30 that covers a portion of the bull gear 15 is formed on the inner surface of the vertical wall 51 of the gear housing 120. The guide cover 30 protrudes from the inner surface of the vertical wall 51 toward the motor cover 43 and has a width w1 (see FIG. 14) the same as the width w2 (see FIG. 14) of the side wall 52 of the gear housing 120. The guide cover 30 is formed to have an inner diameter larger than the diameter of the bull gear 15 and positioned at a predetermined distance from the bull gear 15.

The bull gear 15 rotates counterclockwise in FIG. 15 and substantially the fourth quadrant of the guide cover 30 is cut off in FIG. 15. An oil guide groove 301 is formed on the inner surface of the guide cover 30 in the rotation direction of the bull gear 15. A plurality of oil guide grooves 301 is formed in parallel with the motor shaft 14, at a predetermined distance from each other (see FIG. 14).

Further, a stepped protrusion 53 is formed at the upper portion of the inner surface of the vertical wall 51 of the gear housing 120, that is, on the outer surface of the side of the bull gear 15. The protrusion 53 is stepped down toward the side wall 52. One end of the protrusion 53 is connected to the side wall 52 and the other end is positioned at a predetermined distance from the upper end of the guide cover 30 vertically and horizontally in FIG. 15. The width of the protrusion 53 is the same as the width of the guide cover 30.

When the gear housing 120 described above is fastened to the motor cover 43, the side wall 52, the guide cover 30, and the protrusion 53 are in close contact with the motor cover 43, thereby forming a predetermined internal space. That is, an oil reservoir 32 is formed at the lower portion of the assembly of the gear housing 120 and the motor cover 43, an oil channel is formed between the bull gear 15 and the guide cover 30, and a temporary reservoir 54 collecting the lubricant and circulating again the collected lubricant is formed above the protrusion 53.

Therefore, as the bull gear 15 rotates, the lubricant in the oil reservoir 32 is scattered by the teeth of the bull gear 15, moves along the oil guide grooves 301 formed on the guide cover 30, and drops onto the protrusion 53 by means of the gravity and collects in the temporary reservoir 54. Further, the lubricant collecting in the temporary reservoir 54 is supplied to the second composite bearing 42 of the bull gear 15 and the first composite bearing 26 of the high speed rotation body 20 by the circulation structure, which is described below.

In the structure of the gear housing 120, the guide cover 30 and the protrusion 53 are integrally formed with the gear housing 120. Therefore, it does not need to separately manufacture an oil reservoir and a temporary reservoir and assemble them in the housing and it is possible to easily form the oil reservoir 32 and the temporary reservoir 54 by hermetically fastening the motor cover 43 to gear housing 120.

FIG. 16 is a front view of the turbo blower 100 shown in FIG. 8, seen from the direction C, in which a portion of the outer surface of the housing 120 is shown inside the dotted line.

Referring to FIGS. 15 and 16, a first oil pipe 55 connecting the temporary reservoir 54 with the fixing shaft 41 of the bull gear 15 is formed outside the vertical wall 51 of the gear housing 120. That is, a first through-hole 56 is formed at a position corresponding to the temporary reservoir 54 through the vertical wall 51 of the gear housing 1200 and one end of the first oil pipe 55 is connected to the first through-hole 56. Further, the other end of the first oil pipe 55 is connected with an oil hole 411 formed in the fixing shaft 41.

FIG. 9 shows a portion of the first oil pipe 55 connected to the fixing shaft 41 with a dotted line. Referring to FIG. 9, the first oil pipe 55 supplies lubricant collecting in the temporary reservoir 54 to the oil hole 411 of the fixing shaft 41 and the lubricant supplied to the oil hole 411 lubricates the second composite bearing 42 while sequentially passing the ball bearing 46 and the taper roller bearing 45. Thereafter, the lubricant drops again into the oil reservoir 32 and collects in the oil reservoir 32.

FIG. 17 is a right side view of the turbo blower 110 of FIG. 8, seen from the direction B, in which a portion of the motor cover 43 is cut off to show the inside of the gear housing 120. FIG. 18 is a front view showing the high speed rotation body 20 in the turbo blower 110 shown in FIG. 8.

Referring to FIGS. 17 and 18, a second oil pipe 57 that delivers the lubricant collecting in the temporary reservoir 54 to the high speed rotation body 20 is mounted in the vertical wall 51 of the gear housing 120. For this configuration, a second through-hole 58 is formed at the lower end of the protrusion 53 and one end of the second oil pipe 57 is connected to the second through-hole 58. Further, a third through-hole 59 is formed in the vertical wall 51 of the gear housing 120 which overlaps the rotation body housing 23 and the other end of the second oil pipe 57 is connected to the third through-hole 59.

Further, an oil channel 60 that connects the first composite bearing 26 (the left composite bearing 26 in FIG. 18) at the impeller 22, in the pair of first composite bearing 26, with the third through-hole 59 is formed in the rotation body housing 23. Further, a third oil pipe 61 that connects the first composite bearing 26 (the right first composite bearing 26 in FIG. 18) opposite to the impeller 22 with the oil channel 60 is mounted outside the rotation body housing 23.

Therefore, the lubricant collecting in the temporary reservoir 54 is supplied to the high speed rotation body 20 through the second oil pipe 57 and the supplied lubricant is separately supplied to the first composite bearing 26 at the impeller 22 and the first composite bearing 26 opposite to the impeller 22 through the oil channel 60 and the third oil pipe 61.

The lubricant supplied to the first composite bearing 26 at the impeller 22 lubricates the sliding bearing 24 and the ball bearing 25 while sequentially passing them. A lubricating hole 63 is formed at the support body 62 disposed between the ball bearing 25 and the impeller 22 and the rotation body housing 23 covering it and a fourth oil pipe 64 is mounted outside the rotation body housing 23 to connect the lubricating hole 63 with the gear housing 120. Therefore, the used lubricant flows into the gear housing 120 through the fourth oil pipe 64 and collects in the oil reservoir 32.

Further, the lubricant supplied to the first composite bearing 26 at the opposite side of the impeller 22 through the third oil pipe 61 is supplied to the sliding bearing 24 and the ball bearing 25 to lubricate them, and the used lubricant drops through the cut-off portion exposing the pinion gear 16 at the center of the rotation body housing 23 and collects in the oil reservoir 32.

Returning to FIG. 9, the bearing 65 and the sealing member 66 are disposed in parallel away from the bull gear 15, on the external circumferential surface of the motor shaft 14. The lubricant is also scattered to the motor shaft 14 at high speed while the bull gear 15 rotates, such that the bearing 65 can be sufficiently lubricated by the scattered lubricant. A fifth oil pipe 67 is mounted in the sealing member 66, such that the lubricant that reaches the sealing member 66 through the bearing 65 is returned to the oil reservoir 32.

As described above, it is possible to circulate and supply lubricant to the first composite bearings 26 of the high speed rotation body 20 and the second composite bearings 42 of the bull gear 15, without using a specific oil pump for supplying lubricant, in the turbo blower 110 of the second exemplary embodiment. Therefore, it is possible to simplify the lubricant supply structure and it is possible to reduce the number of parts.

While this invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. 

1. A turbo blower comprising: a motor having a motor shaft; a gear housing accommodating a bull gear fitted on the motor shaft and a pinion gear engaged with the bull gear; a high speed rotation body that includes a rotary shaft having the pinion gear on the external circumferential surface, an impeller fitted on one end of the rotary shaft, and a rotation body housing accommodating the rotary shaft, the pinion gear, and at least one first composite bearing and partially cut off to expose the pinion gear, and is partially accommodated in the gear housing; and a scroll portion covering the impeller and discharging compressed air.
 2. The turbo blower of claim 1, wherein: the first composite bearing includes: a composite bearing block integrally having a sliding bearing block and a ball bearing block; a sliding bearing shaft formed on the external circumferential surface of the rotary shaft and accommodated in the sliding bearing block to form a sliding bearing together with the sliding bearing block; and a ball bearing accommodated in the ball bearing block.
 3. The turbo blower of claim 2, wherein: the first composite bearing is positioned at both sides of the pinion gear and a predetermined gap of the sliding bearing is larger than a predetermined gap of the ball bearing.
 4. The turbo bearing of claim 3, wherein: the sliding bearing shaft has a plurality of oil grooves for forming an oil film on the surface and a plurality of taper grooves which are formed at an angle, and the sliding bearing block has a side pressure-absorbing groove at the portion facing the bull gear, in the inner surface and absorbs side pressure due to the bull gear.
 5. The turbo blower of claim 4, wherein: the high speed rotation body has a vent hole formed at the end of the rotation body housing which faces the impeller, the pinion gear is formed in a helical gear shape, and the direction of the helical gear is determined such that a force attracting the rotary shaft in opposite direction to the impeller when the rotary shaft rotates.
 6. The turbo blower of claim 1, wherein: the gear housing has an arc-shaped guide cover having a plurality of oil guide grooves on the inner surface while covering a portion of the bull gear, and an oil box connected with the end of the guide cover at the upper portion therein.
 7. The turbo blower of claim 6, wherein: the gear housing has an oil pipe therein to supply lubricant collecting in the oil box to the first composite bearing, one end of the oil pipe is connected with an oil outlet formed in the oil box, and the other end of the oil pipe is connected with an oil inlet formed in the first composite bearing.
 8. The turbo blower of claim 7, wherein: the rotation body housing has a vapor outlet for discharging oil vapor, the turbo blower further includes an oil vapor cooler connected with the vapor outlet and the oil box, and the oil vapor cooler supplies the oil vapor discharged to the vapor outlet to the oil box after condensing the oil vapor.
 9. The turbo blower of claim 8, wherein: the gear housing has an oil reservoir at the lower portion, the oil reservoir has a pair of holes at the upper and lower portion of the side wall, and the gear housing further includes a connection pipe connecting the pair of holes and a control valve disposed in the connecting pipe.
 10. The turbo blower of claim 6, wherein: the bull gear is directly fitted on the motor shaft, the gear housing has a combining surface with an opening larger than the diameter of the bull gear, at the side facing the motor, and the combining surface is combined with the motor.
 11. (canceled)
 12. A high speed rotation body comprising: a rotary shaft having a pinion gear engaged with a bull gear, on the external circumferential surface; an impeller fitted on one end of the rotary shaft; a pair of first composite bearings disposed at both sides of the pinion gear; and a rotation body housing accommodating the rotary shaft, the pinion gear, and the pair of first composite bearings, and partially cut off to expose the pinion gear.
 13. The high speed rotation body of claim 12, wherein: each of the pair of first composite bearings includes: a composite bearing block integrally having a sliding bearing block and a ball bearing block; a sliding bearing shaft formed on the external circumferential surface of the rotary shaft and accommodated in the sliding bearing block to form a sliding bearing together with the sliding bearing block; and a ball bearing accommodated in the ball bearing block.
 14. The high speed rotation body of claim 13, wherein: a predetermined gap of the sliding bearing is larger than a predetermined gap of the ball bearing, the sliding bearing shaft has a plurality of oil grooves for forming an oil film on the surface and a plurality of taper grooves which are formed at an angle, and the sliding bearing block has a side pressure-absorbing groove formed in the opposite direction to the direction of side pressure in order to absorb the side pressure due to the bull gear, on the inner surface.
 15. A turbo blower comprising: a motor having a motor shaft; a bull gear detachably fitted on the motor shaft and having a hole for mounting a fixing shaft at the center; a second composite bearing disposed between the fixing shaft and the bull gear and having a taper roller bearing and a ball bearing that are parallel with the motor shaft; and a high speed rotation body having a rotary shaft with a pinion gear engaged with the bull gear, on the external circumferential surface, and an impeller fitted on one end of the rotary shaft.
 16. The turbo blower of claim 15, further comprising: a motor cover fastened to the motor and supporting the motor shaft; and a gear housing accommodating the bull gear and the pinion gear and having an opening having a diameter larger than the diameter of the bull gear, at the side fastened to the motor cover.
 17. The turbo blower of claim 16, wherein: the motor shaft has a flange on the external circumferential surface of the end facing the bull gear, the bull gear is fastened to the motor shaft by a plurality of bolts passing through the bull gear and the flange, and the gear housing has an opening at the portion facing any one bolt in the plurality of bolts.
 18. The turbo blower of claim 16, wherein: the motor cover has a recess protruding toward the motor to accommodate a portion of the high speed rotation body in the recess.
 19. The turbo blower of claim 16, wherein: the high speed rotation body further includes: a pair of first composite bearing disposed at both sides of the pinion gear; and a rotation body housing accommodating the rotary shaft and the pair of first composite bearing, assembled with the gear housing, and partially cut off to expose the pinion gear in the gear housing.
 20. The turbo blower of claim 19, wherein: each of the first composite bearings includes: a composite bearing block integrally having a sliding bearing block and a ball bearing block; a sliding bearing shaft formed on the external circumferential surface of the rotary shaft and accommodated in the sliding bearing block to form a sliding bearing together with the sliding bearing block; and a ball bearing accommodated in the ball bearing block.
 21. The turbo blower of claim 20, wherein: a predetermined gap of the sliding bearing is larger than a predetermined gap of the ball bearing and the sliding bearing shaft has a plurality of oil grooves for forming an oil film on the surface and a plurality of taper grooves which are formed at an angle.
 22. The turbo blower of claim 19, wherein: the gear housing has an arc-shaped guide cover covering a portion of the bull gear, on the inner surface, and a stepped protrusion positioned on the outer surface of the side of the bull gear, and the protrusion forms a temporary reservoir in an assembly of the gear housing and the motor cover.
 23. The turbo blower of claim 22, wherein: the guide cover has a plurality of oil guide grooves connected long in the rotation direction of the bull gear, on the inner surface.
 24. The turbo blower of claim 22, wherein: the gear housing further includes a first through-hole at the portion where the temporary reservoir is formed and a first oil pipe connecting the first through-bole with the fixing shaft at the outside of the gear housing.
 25. The turbo blower of claim 24, wherein: the fixing shaft is fastened to the gear housing, the fixing shaft has an oil holes therein, and an oil channel is formed between the fixing shaft and the motor shaft, such that lubricant supplied to the oil hole is guided to the second composite bearing.
 26. The turbo blower of claim 22, wherein: the protrusion has a second through-hole at the lower end, the gear housing has a third through-hole at the joint with the rotary shaft housing, and a second oil pipe connecting the first through-hole with the third through-hole in the gear housing is further included.
 27. The turbo blower of claim 26, wherein: the rotation body housing has an oil channel connecting the first composite bearing at the impeller in the pair of first composite bearing with the third through-hole, and further includes a third oil pipe connecting the first composite bearing at the opposite side of the impeller in the pair of first composite bearing with the oil channel at the outside thereof.
 28. The turbo blower of claim 27, wherein: the high speed rotation body further includes a support body disposed between the first composite bearing at the impeller and the impeller, the support body and the rotation body housing form an oil outlet, and the rotation body housing further includes a fourth oil pipe connecting the oil outlet with the gear housing at the outside to collect the lubricant.
 29. The turbo blower of claim 25, further comprising: a bearing and a sealing member that are disposed in parallel away from the bull gear, on the external circumferential surface of the motor shaft; and a fifth oil pipe connecting the sealing member with the inside of the motor cover to collect lubricant reaching the sealing member.
 30. A turbo blower comprising: a motor having a motor shaft and assembled with a motor cover; a bull gear detachably fitted on the motor shaft and having a hole for mounting a fixing shaft at the center; a high speed rotation body including a rotary shaft having a pinion gear engaged with the bull gear, on the external circumferential surface, an impeller fitted on one end of the rotary shaft, at least one first composite bearing supporting the rotary shaft, and a rotation body housing accommodating the rotary shat and the first composite bearing and partially cut off to expose the pinion gear; a second composite bearing disposed between the fixing shaft and the bull gear and having a taper roller bearing and a ball bearing that are parallel with the motor shaft; a gear housing accommodating the bull gear and the pinion gear and having an opening having a diameter larger than the diameter of the bull gear, at the side fastened to the motor cover; and a scroll portion covering the impeller and discharging compressed air. 